[SOLVED] bash script - return full path and filename

rainbowbird · 06-22-2009, 03:27 AM

Quote:

Originally Posted by Disillusionist

Code:

source="./tmp/myfile"
dest=~/.Waste/$(echo $source|sed "s@^./@$PWD@"|sed "s@^/@@")

Disillusionist:
a little modifiation

Code:

source="./tmp/myfile"
dest=~/.Waste/$(echo $source|sed "s@^./@$PWD/@"|sed "s@^/@@")

kj6loh · 09-07-2009, 02:34 PM

Quote:

Originally Posted by Andy Alkaline

I'd like to be able to move the file into ~/.Waste/original/path

Using $PWD doesn't guarantee that. I need to have the absolute path of the file returned.

(a few minutes later)
Found it.
Bash equivalent for PHP realpath()

Unfortunately readlink is not on every bash system

edvalson · 11-02-2009, 06:55 PM

Quote:

What is your concern with using $PWD? If concerned about someone exporting variables to an incorrect value, you could always use $(pwd) to set the value of PWD.

Because if you write scripts using absolute paths that are not depending on a) where the script starts from, or b) from cd'ing somewhere inside the script, $PWD is irrelevant.

ta0kira has it right: to return the absolute path of a filename that is originally given with a relative path:

for example you are at a bash prompt in /dir1/dir2/dir3/dir4

and the file is /dir1/dir2/file1

ABSOLUTE_DIR=$(dirname $(readlink -f ../../dir2/file1))

kwutchak · 08-25-2010, 05:16 AM

echo "Absolute path: `cd $1; pwd`"

http://peasleer.wordpress.com/2007/0...-path-in-bash/

catkin · 08-25-2010, 10:50 AM

Another solution is to use the external pwd command instead of the bash builtin. In the following illustration /home/c/Templates is a symlink to /home/c/d/Templates

Code:

c@CW9:~$ ls -l Templates
lrwxrwxrwx 1 c users 11 2010-06-07 11:43 Templates -> d/Template
c@CW9:~$ cd Templates
c@CW9:~/Templates$ pwd
/home/c/Templates
c@CW9:~/Templates$ echo $PWD
/home/c/Templates
c@CW9:~/Templates$ /bin/pwd
/home/c/d/Templates

Andy Alt · 12-28-2010, 02:58 PM

I didn't know readlink was nonstandard. Thanks to the suggestions, this is what I've come up with.

Code:

#!/bin/bash
# abspath.sh
# Find absolute path of file or symbolic link without using readlink
# December 28, 2010

function absp() {
  local FILE=$1
  local CWD=$(pwd)
  
  # remove trailing slash
  FILE=${FILE%/}

  local FBN=`basename "$FILE"`

  # Remove basename to get relative path

  local RP="${FILE%$FBN}"
  
  # change dir to relative path to run pwd
  cd "$RP"

  # Assign present working dir to $MOVETO; pwd returns the
  # absolute path
  AP=$(pwd)
	
  # Append filename to abs path
  APFN=$(pwd)/$FBN

  # Change back to directory we started in
  cd "$CWD"
  
#  echo -e "\n\tAbsolute path:"
#  echo -e "\t$AP"
#  echo -e "\n\tAbsolute path to file:"
#  echo -e "\t$APFN\n"
  
  return 0
}

absp $1
echo -e "\n\tAbsolute path:"
echo -e "\t$AP"
echo -e "\n\tAbsolute path to file:"
echo -e "\t$APFN\n"
exit 0

Andy Alt · 12-28-2010, 03:53 PM

I like this better:

Code:

#!/bin/bash
# abspath.sh 0.01
# Find absolute path of file or symbolic link without using readlink
# December 28, 2010

function absp() {

# Call this function by
# VAR=`absp <filename> ap|apfn>` # backticks required
# ap will return absolute path; apfn will return absolute path with filename

  local FILE=$1
  local CWD=$(pwd)
  
  # remove trailing slash
  FILE=${FILE%/}

  local FBN=`basename "$FILE"`

  # Remove basename to get relative path

  local RP="${FILE%$FBN}"
  
  # change dir to relative path to run pwd
  cd "$RP"

  # Assign present working dir to $MOVETO; pwd returns the
  # absolute path
  local AP=$(pwd)
	
  # Append filename to abs path
  local APFN=$(pwd)/$FBN

  # Change back to directory we started in
  cd "$CWD"
  
  case $2 in
  ap)
  echo "$AP"
  ;;
  apfn)
  echo "$APFN"
  ;;
  *)
  echo "NULL";return 1;break
  ;;
  esac
  
  return 0
}

# absp function takes two parameters; file name and ap|apfn
# This method allows different variable names for AP or APFN throughout the program

ABSOLUTE_PATH=`absp $1 ap`
ABSOLUTE_FILE=`absp $1 apfn`

echo $ABSOLUTE_PATH
echo $ABSOLUTE_FILE

exit 0

Andy Alt · 01-24-2011, 02:50 AM

I made another change. In the previous function I posted, it has to be called three times if the absolute path, absolute path with filename, and base filename are required. That can slow things down. This method may be slightly more memory intensive, but speeds up the process.

Code:

function gfp_info() {

  local FILE=$1
  
  # save pwd to cd back to it below
  local CWD=$(pwd)
  
  # remove trailing slash
  FILE=${FILE%/}

  # Get the basename of the file
  local file_basename=`basename "$FILE"`

  # Remove basename to get relative path
  # Using bash's string function instead of calling
  # dirname
  local RP="${FILE%$file_basename}"

  # change dir to relative path
  cd "$RP"

  # Assign present working dir to $fileap; pwd returns the
  # absolute path
  local fileap=$(pwd)
	
  # Append base filename to absolute path
  local ap_with_basename=$(pwd)/$file_basename

  # Change back to directory we started in
  cd "$CWD"
  
  AP="${fileap}"
  APFN="${ap_with_basename}"
  FBN="${file_basename}"

  return 0

}

# Initialize variables used in function so they can be used globally
AP=""
APFN=""
FBN=""

gfp_info "$FILENAME"

# The three variables above will now have value.

catkin · 01-24-2011, 10:50 AM

It could go a little faster if:

local CWD=$(pwd) was removed and cd "$CWD" was changed to cd -
file_basename=`basename "$FILE"` was changed to file_basename="${FILE##*/}"
fileap=$(pwd) was changed to fileap=$PWD
ap_with_basename=$(pwd)/$file_basename was changed to ap_with_basename=$fileap/$file_basename or ap_with_basename=$PWD/$file_basename. In the latter case $fileap need not be used if suggestion 6 is implemented.
AP=""
APFN=""
FBN=""
were removed; these variables are created as global variables by assigning values to them in the function.
AP="${fileap}" were moved prior to cd "$CWD" in which case $fileap need not be used if suggestion 4, second option is implemented.

Incidentally ...

pwd does not return the absolute path if the path was reached via a symlink in which case pwd -P is needed:

Code:

c@CW8:~$ cd /tmp
c@CW8:/tmp$ mkdir foo
c@CW8:/tmp$ ln -s foo bar
c@CW8:/tmp$ cd bar
c@CW8:/tmp/bar$ pwd
/tmp/bar
c@CW8:/tmp/bar$ pwd -P
/tmp/foo

RP="${FILE%$file_basename}" does not generate a relative path; it extracts the directory component of the full path. A relative path is one that does not begin with "/". The same could be achieved by the common idiom RP=${FILE%/*} (the double quotes are not necessary on the RHS of an assignment "=". Strictly speaking these are not "bash string functions" but bash parameter expansions.

catkin · 01-24-2011, 10:51 AM

Quote:

Originally Posted by catkin

Another solution is to use the external pwd command instead of the bash builtin.

That works but using the pwd builtin with the -P option is faster.

Andy Alt · 01-25-2011, 03:39 PM

I've made the changes to my script, with some exceptions.

cd "-" &>/dev/null

And when I was using rmw on a file in my present working directory, RP=${FILE%/*} would kick out an error. (No slash to find)

Thanks for the suggestions, catkin. Good stuff.

catkin · 01-26-2011, 03:28 AM

Quote:

Originally Posted by Andy Alkaline

And when I was using rmw on a file in my present working directory, RP=${FILE%/*} would kick out an error. (No slash to find)

Strange; it should silently do nothing as in

Code:

c@CW8:/tmp$ FILE=foo
c@CW8:/tmp$ var=${FILE%/*}
c@CW8:/tmp$ echo $var
foo

Andy Alt · 01-26-2011, 01:20 PM

I was wrong about the slash, but the code you suggested assigns the basename, whereas I want everything except for the basename. Since I'm not good at explaining, allow me to illustrate:

Code:

  # extracts the directory component of the full path
#  local DC="${FILE%$file_basename}"
  local DC="${FILE%/*}"
  echo -e $c_1"FILE: $FILE"$c_reset
  cd "$DC"
  echo -e $c_1"DC: \"$DC\" pwd: - \"$(pwd -P)\" "$c_reset
  # Assign present working dir to $fileap; pwd returns the
  # absolute path
  local fileap=$(pwd -P)

andy@pigeon:~/Documents$ rmw temp
FILE: temp
/home/andy/bin/rmw: line 451: cd: temp: Not a directory
DC: "temp" pwd: - "/home/andy/Documents"
`temp' -> `/home/andy/.Waste/files/temp.2011-01-26h13m11s43'

---

Code:

  # extracts the directory component of the full path
  local DC="${FILE%$file_basename}"
#  local DC="${FILE%/*}"
  echo -e $c_1"FILE: $FILE"$c_reset
  cd "$DC"
  echo -e $c_1"DC: \"$DC\" pwd: - \"$(pwd -P)\" "$c_reset
  # Assign present working dir to $fileap; pwd returns the
  # absolute path
  local fileap=$(pwd -P)

andy@pigeon:~/Documents$ rmw temp
FILE: temp
DC: "" pwd: - "/home/andy/Documents"
`temp' -> `/home/andy/.Waste/files/temp.2011-01-26h13m14s23'

I've added an if clause around cd $DC

Code:

if [ $DC ]; then  
    cd "$DC"
  fi

If in the same dir as the file, no need to tell cd to change to nothing and waste everyone's time.

catkin · 01-26-2011, 11:41 PM

For the basename: basename=${fullpath##*/}. It looks like this at the command prompt:

Code:

c@CW8:/tmp$ fullpath=/etc/rsyncd.conf
c@CW8:/tmp$ basename=${fullpath##*/}
c@CW8:/tmp$ echo $basename
rsyncd.conf

Andy Alt · 01-27-2011, 09:37 AM

Code:

function gfp_info() {

# Thanks to catkin for the massive improvements to this function
# http://www.linuxquestions.org/questions/user/catkin-444761/

  local FILE=$1
  
  # remove trailing slash
  FILE=${FILE%/}

  # Get the basename of the file
  local file_basename="${FILE##*/}"

  # extracts the directory component of the full path
  local DC="${FILE%$file_basename}"

  if [ $DC ]; then  
    cd "$DC"
  fi

  # Assign present working dir to $fileap; pwd returns the
  # absolute path
  local fileap=$(pwd -P)
	
  # Append base filename to absolute path
  local ap_with_basename=$fileap/$file_basename

  # Change back to directory we started in
  cd "-" &>/dev/null
  
  AP="${fileap}"
  APFN="${ap_with_basename}"
  FBN="${file_basename}"

  return 0

}